The proposal seeks support for the first large-scale longitudinal investigation of daily stressors and well-being during adulthood. The primary goal is to examine how sociodemographicfactors, hearth status, personality characteristics,and genetic endowment modify patterns of change in exposure to day-to-day life stressors as well as physical and emotional reactivity to these stressors. The aims are to : (1) describe how the links between multiple aspects of daily stressors (e.g., frequency, content, severity) and daily physical and emotional well-being change over 10 years during adulthood; (2) examine how personal factors, including sociodemographic factors and personality characteristics influence change in both exposure to as well as changes in physical and emotional reactivity to daily stressors; (3) investigate how exposure and reactivity to daily stressors correlate with physiological indicators of physical health and predict changes in global health reports; and (4) explore the relativegenetic and environmental influences mediating change in exposure and physical and emotional reactivity to dally stressors throughout adulthood. These aims will be addressed by collecting a second wave of the National Study of Daily Experiences (NSDE) approximately 10 years after the first data collection. The NSDE is a telephone diary study of a U.S. national sample of 1483 adults ranging in age from 25 to 74 years. Respondents in the NSDEare a representative subsample of the MIDUS (Midlife in the United States) survey. A rich set of prospective and concurrent sociodemographic, physical health, and personality measures assessed by the MIDUS survey will be used to predict change in exposure and physical and emotional reactivity to daily stressors from Time 1 to Time 2 of the NSDE. In addition, data from the proposed MIDUS biological project would allow us to examine how daily stress processes measured in the proposed NSDE collection are related to physiological indicators of health (e.g., allostatic load, immune functioning). All of these questions will be examined in a genetically informativesample to test how these processes are mediated by both genetic and environmental influences.